NVH development aspects of DI gasoline engines

The application of direct injection (DI) technology to gasoline engines reduces fuel consumption considerably, especially due to stratified lean operation at part load. However, stratified lean operation increases NVH excitation which is incompatible with increasing costomer demand for high automotive comfort. This article of FORD and FEV Motorentechnik discusses the influence of DI technology on NVH behavior of gasoline engines. Aside from process caused NVH relevant effects due to the combustion process, flow noise and cyclic speed fluctuation during stratified operation, the effects of the highpressure injection system and the specific DI piston design are examined.